Visual Nastran Research Articles

Design and Numerical Characterization of a Human Ankle Prosthesis

This paper addresses to a finite element analysis in dynamic conditions of a human ankle joint prosthesis based on a cam mechanism design. The proposed ankle joint prosthesis mechanism is a parameterized one and was designed in order to fulfil main human locomotion tasks namely walking during daily activities. A proper 3D CAD model has been developed and the proposed cam mechanism ankle prosthesis was modelled and simulated into MSC Visual Nastran environment. Results of simulations demonstrate the engineering feasibility of the design and validate the proposed parameterized prototype.

Simulation and control of multipurpose wheelchair for disabled/elderly mobility

© 2016 IOS Press and the author(s). This paper presents investigations into the development of modelling and control strategies for a multipurpose wheelchair as mobile transporter for elderly and disabled people. The research is aimed at helping people with physical weakness/disabilities in their upper and lower extremities to move independently without human intervention. A novel reconfiguration which allows multi-task operations in the same wheelchair system with improved design is modelled in Visual Nastran 4D (VN4D) software. A modular fuzzy logic control mechanism with integrated phases is introduced for the overall operations and two-wheeled stabilization of the wheelchair. It is shown that the proposed modular fuzzy control approach is able to ensure system stability while performing multipurpose tasks such as manoeuvrability on flat surfaces, stairs climbing (ascending and descending), standing in the upright position on two wheels and transformation back to standard four wheels with up to 50% less initial torque in comparison to previous designs.

Sit-to-Stand and Stand-to-Sit Control Mechanisms of Two-Wheeled Wheelchair.

This paper presents a mechanism for standing and sitting transformation of a wheelchair using a two-wheeled inverted pendulum concept with reduced torque requirement, in simulation studies. The motivation of this work is to design a compact standing mechanism to help an elderly/disabled person with functional limitation in lower extremities to maneuver in small and confined spaces and enable them to perform standard daily life routines independently. The wheelchair system at the upright standing position is tested with different travel distances, and the challenge is to control both sit-to-stand and stand-to-sit operations in a stable manner using flexible-joint humanoid. An additional spring/damping element is incorporated at each wheel to provide a comfortable ride for the user especially during stand-to-sit transformation task. A PD-fuzzy control with modular structure is implemented, and the performance of the system is observed through visual nastran 4d (vn4d) visualization software and simulation in matlab. The stand-to-sit performance tests have shown more than 38% reduction in tilt and back seat angles fluctuation in linear travel motion using a suspension system, while the initial tilt torque needed is 50% less than the amount required in previous designs.

Design, manufacture and evaluation of a new flexible constant velocity mechanism for transmission of power between parallel shafts

This paper presents a new mechanism (coupling) for power transmission between parallel shafts in more ranges. The mechanism consists of one drive shaft and one driven shaft, 3 S-shape transmitter links and 8 connecting links. The advantage of this mechanism is that the velocity ratio between input and output shafts remains constant at all movements, and its capacity to offset misalignments is greater than that of other couplings. This research also includes a kinematic analysis and simulations using Visual NASTRAN, Autodesk inventor dynamic and COSMOS motion to prove that the mechanism exhibits a constant velocity. Finally, the mechanism was fabricated and evaluated; results showed that the mechanism can practically transmit a constant velocity ratio.

Modelling and Investigation on Bouncing Mechanism of a Sphere Robot

Spherical rolling mechanisms (SRMs) exhibit a number of advantages with respect to wheeled and legged mechanisms. In fact if the SRM is combined with the power of bouncing mechanism, it will produce an exciting phenomena that can be contributed to applications such as security surveillance, search and rescue. There is not much research done in both fields, especially in the bouncing mechanism. In fact to the best of authors’ knowledge no of research has been done on integrating both mechanism to produce a spherical system that is capable of rolling and bouncing, which can produce a very significant mobile robot. Therefore, this research deals with the modeling and development of a bouncing spherical robot using computational intelligent technique, i.e. Particle Swarm Optimization technique (PSO). A 3D virtual prototype of a spherical robot was developed in Visual Nastran as a platform for input and out data acquisition. Different simulations environment have been created, such as the free fall bouncing, shooting up and projectile type of environment to investigate the bouncing profile affected by different forces. The data obtained were then used for system identification using PSO technique with mean square error (MSE) of 0.0004%. The transfer function representing the bouncing mechanism of the sphere robot was then obtained. Next, the prototype of the sphere robot with bouncing capability was developed. Open loop tests have been conducted and the results show that the hardware developed can produce the bouncing mechanism at its promising capability. Future works need to be conducted to re-visit the hardware, particularly on the body of the sphere robot such that maximum bouncing can be achieved.

Design, Construction and Evaluation of Potato Digger with Rotary Blade

Abstract Potato has an important role in human food. It was the sixth alimentary product in the world after sugar cane, maze, rice, wheat and milk in 2011 year. In addition, potato is the third product in Iran after wheat and sugar cane in 2011 year. Therefore, any attempt in the improvement of potato harvester will be valuable. In this study, a new semi-mounted one-row potato digger with rotary blade was designed and made in the workshop of Shahrekord University. It can be connected to rotary potato graders. Transmission system was mechanical from tractor (PTO) to blade by belt, pulley, gearbox, chain and sprocket. Blade diameter was 76 cm and the length was 10 cm which was assigned by the researchers. For separating of soil from potato, a helix containing bars with 2.6 cm distance and diameter of 9 mm was applied. Entered soil into set was calculated as 227 ton/h. Required power was got 5.5 horsepower. Computerized model of set was prepared in Mechanical Desktop Software and potato motion was studied in Visual Nastran Software. The device was tested at field with various advance speed, blade angle and rotational speed. Results showed that advance speed of 1.5-3 km/h, rotational speed of 20-25 RPM and blade angle of 10- 15° were proper for system. The average of damaged potatoes was 4%.

Trajectory Planning and Walking Pattern Generation of Humanoid Robot Motion

Walking trajectory generation for a humanoid robot is a challenging control issue. In this paper, a walking cycle has been recognized considering human motion, and nine simple steps were distinguished in a full step of walking which form motion trajectory, and generates a simplified ZMP motion formulation. This system was used in humanoid robot simulation motion and is achievable easily in walking steps of robot. A minimum DOFs humanoid robot has been considered and geometrical relationships between the robot links were presented by the Denavit-Hartenberg method. The inverse kinematics equations have been solved regarding to extracted ZMP trajectory formula, and constraints in different steps. As a result; angular velocity, acceleration and power of motors were obtained using the relationships and Jacobin. At each step, extracted data were applied on simulated robot in Matlab, and Visual Nastran software. Zero moment point trajectory was evaluated in simulation environment.

The Study of Rolling Temperature Condition Influence on the Formation of Hot Strip Cross-Section Rolled on the Longitudinal-Wedge Mill

The mill of new construction is proposed in the article. To calculate the specialized metal forming processes the software of finite element analysis - MSC Super Forge MSC Visual Nastran 4D was used. Stress-strain state (SSS) of the rolled workpiece and heavy-loaded units of the proposed mill was calculated. The influence of the rolling temperature regimes on formation of hot-rolled strips cross-section was investigated. The hot-rolled strips were rolled on longitudinal wedge mill. It is proved that the workpiece is deformed in the conditions of soft SSS in a mill of new construction, in other words the amount of the elastic deformation and displacement of the rolls units are small. The investigation has also proved sufficiently high fixity of the joints of roller assembly work stand as well as that the equivalent voltage does not exceed the maximum permissible value for the material strength in heavy-loaded units of the mill.

Influence of Thermal Condition Prorollers to Formation of Cross-Section Profile of Hot-Rolled Strips, Rolled on the Longitudinal -Wedge Mill

This paper proposes a new design of mill. Using the software of finite element (FE) analysis, specialized for the calculation of metal forming processes MSC. SuperForge и MSC, visual Nastran 4D, calculated the stress-strain state (SSS) rolled billet and heavy-duty elements of the proposed mill. It is proved that when a new rolling mill thin strips deforming force reduced, the amount of elastic deformation and displacement rolls are small elements. The investigation has also shown that sufficiently high rigidity roller assembly work stand and resulting in heavy-duty elements of the equivalent voltage does not exceed the maximum allowable values, for the material strength.

Determination and analysis of the head and chest parameters by simulation of a vehicle–teenager impact

This paper reports the results of multi-body numerical simulation of a vehicle crash with a teenager pedestrian. A previous technique utilized for adult pedestrian impact is applied. The work starts with the determination of the masses for the various segments of the body of a teenager with a total mass of 45 kg and then switches to the construction of the dummy and the middle-class vehicle in the Visual Nastran environment. Simulations are performed for both frontal impacts and lateral impacts, when the vehicle is travelling at a constant speed and when the vehicle is braking, following the Euro NCAP rules on the subject. The results are analysed by calculating the values of the head injury criterion for the head and the values of the thoracic trauma index and 3 ms criterion for the chest; the injuries are assessed according to the current interpretation. Abbreviated injury scale curves are used to determine the dangerousness of the impact. Finally, the results are close to those obtained by applying the same technique to an adult pedestrian and other available data in the literature for an adult or a child.

PD-fuzzy Control of a Stair Climbing Wheelchair

This paper focuses on the development of a control strategy of a compact stair climbing wheelchair to maintain stable and balance while negotiating staircases in confined spaces for the elderly and disabled. The Visual Nastran 4D is used to develop a simulation models and linked with Matlab platform for control and visual assessment purposes. The challenges are to control front and rear motors as well as tilt angle to ensure system stability and maintain smoothness of the climbing process. PD-Fuzzy controls are developed, tested and associated performances are assessed through intensive visual approach.

Control of a stair climbing wheelchair

This paper presents investigations into the control of a stair climbing wheelchair particularly for indoor usage. A virtual wheelchair model is developed using Visual Nastran software and linked with Matlab/Simulink for control purposes. The goals are to have a simple, compact and stable stairs climbing wheelchair in order to complete the ascending and descending tasks. The challenges are to ensure the wheelchair seat always stay at the upright position and to control both the front and rear wheel motors while climbing. PID control is used to provide appropriate torque to both front and rear wheels as well as at to the wheelchair seat during climbing. Results show that the wheelchair movement can be controlled smoothly and the seat maintained at the desired position with the adapted approach.

EVOLUTIONARY TUNING OF MODULAR FUZZY CONTROLLER FOR TWO-WHEELED WHEELCHAIR

In this work, an optimization technique is adopted to manipulate the input and output scaling factors of a modular fuzzy logic controller (MFC) for lifting and stabilizing the front wheels of a wheelchair in two-wheeled mode. A virtual wheelchair (WC) model is developed within Visual Nastran (VN) software environment where the model is further linked with Matlab/Simulink for control purposes. The lifting of the chair is done by transforming the first link (Link1), attached to the front wheels (casters) to the upright position while maintaining stability of the second link (Link2) where the payload is attached. General rules of thumb allow heuristic tuning (trial and error) of the parameters but such heuristic method does not guarantee that the system tuned with current data set will represent future system states. A global optimization mechanism such as genetic algorithm is necessary to improve the system performance. Due to its significant advantages over other searching methods, a genetic algorithm approach is used to optimize the scaling factors of the MFC and results show that the optimized parameters give better system performance for such a complex, highly nonlinear two-wheeled wheelchair system.

Simulation of Chain Drive Based on MSC. Visual Nastran 4D

In the distance learning of the courses of Machine Parts and Design, the hypothesized experiment through internet is a kind of the significance teaching method. At present, multimedia, network technologies are extremely mature. Using the internet technology to realize the course learning can help the students to master the principle of chain drive easily. The key problem to realize the hypothesized experiment on the net is how to carry on the simulation of machine parts or components using the computer software. The realization method of the hypothesized simulation of chain drive is introduced in this paper based on MSC. Visual Nastran 4D software.

Design, manufacture and evaluation of a new and simple mechanism for transmission of power between intersecting shafts up to 135 degrees (Persian Joint)

This paper introduces a new mechanism which is designed for the transmission of power between two intersecting shafts. The mechanism consists of one drive shaft and one driven shaft, six guide arms, and three connecting arms. The intersecting angle between the input shaft and the output shaft can be varied up to 135° while the velocity ratio between the two shafts remains constant. The research also includes a kinematic analysis and a simulation using Visual NASTRAN, Autodesk Inventor Dynamic and COSMOS Motion. The softwares showed that this mechanism can transmit constant velocity ratios at all angles between two shafts. By comparing the graphs of analytical analysis and simulation analysis, validity of equations was proved. Finally, by fabrication and evaluation of the mechanism it was shown that this mechanism can transmit constant velocity practically.

A Modular Fuzzy Control Approach for Two-Wheeled Wheelchair

Wheelchairs on two wheels are becoming essential part of life for disabled persons. But designing control strategies for such wheelchairs is a challenging task due to the fact that they are highly nonlinear and unstable systems. The subtle design of the system mimics a double inverted pendulum with three actuators, one for each wheel, and one for chair position. The system starts to work with lifting the front wheels (casters) to the upright position and further with stabilizing in the upright position. The challenge resides in the design and implementation of suitable control strategies for the two-wheeled wheelchair so as to perform comparably similar to a normal four-wheeled wheelchair. A two-level modular fuzzy logic controller is proposed in this paper. A model of the standard wheelchair is also developed as a test and verification platform using Visual Nastran software integrated with Matlab.

FES-Assisted Walking with Spring Brake Orthosis: Simulation Studies

This paper presents a simulation of bipedal locomotion to generate stimulation pulses for activating muscles for paraplegic walking with wheel walker using functional electrical stimulation (FES) with spring brake orthosis (SBO). A new methodology for paraplegic gait, based on exploiting natural dynamics of human gait, is introduced. The work is a first effort towards restoring natural like swing phase in paraplegic gait through a new hybrid orthosis, referred to as spring brake orthosis (SBO). This mechanism simplifies the control task and results in smooth motion and more-natural like trajectory produced by the flexion reflex for gait in spinal cord injured subjects. SBO can eliminate reliance on the withdrawal reflex and foot-ground clearance without extra upper body effort. The stored energy in the spring of SBO is used to replace stimulation pulses in knee flexion and reduce total required torque for the paraplegic walking with wheel walker. The study is carried out with a model of humanoid with wheel walker using the Visual Nastran (Vn4D) dynamic simulation software. Stimulated muscle model of quadriceps is developed for knee extension. Fuzzy logic control (FLC) is developed in Matlab/Simulink to regulate the muscle stimulation pulse-width required to drive FES-assisted walking gait and the computed motion is visualised in graphic animation from Vn4D. The simulation results show that SBO can be successfully used with FES for paraplegic walking with wheel walker with all the advantages discussed over the current hybrid orthoses available.

FES-Assisted Walking with Spring Brake Orthosis: Simulation Studies

This paper presents a simulation of bipedal locomotion to generate stimulation pulses for activating muscles for paraplegic walking with wheel walker using functional electrical stimulation FES with spring brake orthosis SBO. A new methodology for paraplegic gait, based on exploiting natural dynamics of human gait, is introduced. The work is a first effort towards restoring natural like swing phase in paraplegic gait through a new hybrid orthosis, referred to as spring brake orthosis SBO. This mechanism simplifies the control task and results in smooth motion and more-natural like trajectory produced by the flexion reflex for gait in spinal cord injured subjects. SBO can eliminate reliance on the withdrawal reflex and foot-ground clearance without extra upper body effort. The stored energy in the spring of SBO is used to replace stimulation pulses in knee flexion and reduce total required torque for the paraplegic walking with wheel walker. The study is carried out with a model of humanoid with wheel walker using the Visual Nastran Vn4D dynamic simulation software. Stimulated muscle model of quadriceps is developed for knee extension. Fuzzy logic control FLC is developed in Matlab/Simulink to regulate the muscle stimulation pulse-width required to drive FES-assisted walking gait and the computed motion is visualised in graphic animation from Vn4D. The simulation results show that SBO can be successfully used with FES for paraplegic walking with wheel walker with all the advantages discussed over the current hybrid orthoses available.

Comparação entre dois tipos de suspensão passiva de barra em condições simuladas de pista de prova normalizada

Neste trabalho, foram feitas algumas análises sobre o comportamento dinâmico simulado de dois tipos de suspensões passivas das barras dos pulverizadores tracionados. Estas análises foram conduzidas em condições virtuais de pista de prova normalizada ISO 5008, com dois níveis de velocidade de deslocamento do pulverizador (5 km h-1 e 15 km h-1) e em dois perfis de pista existentes na norma (acidentada e suavizada). Foram utilizados nas simulações os softwares MATLAB®; SIMULINK® e Visual Nastran®. Os resultados mostram que a suspensão do tipo trapezoidal teve melhor desempenho em baixas frequências de excitação (w < 0,2 Hz), enquanto a suspensão do tipo pêndulo simples teve melhor desempenho nas demais condições das pistas normalizadas.

English

This paper deals with rotating bending fatigue tests at high speed (150 Hz) carried out on AISI-SAE 1018 steel with a high content of impurities (non metallic inclusions), for which the high experimental stress inside the specimen is close to the elastic limit of the material. Simulations of rotating loading are obtained by Visual NASTRAN software in order to determine the numerical stresse and strain distributions inside a hypothetical homogeneous specimen; later, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed and then, the experimental results are presented and discussed according the observed failure origin related to the non metallic inclusions and the associated high stress zones. Finally, a simple model is proposed to predict the fatigue life for this non homogeneous steel under high speed rotating bending fatigue tests close to the elastic limit, based on the rate between the visual macro-plastic deformation zone at fracture surface and the total fracture surface, together with the crack initiation inclusion (or inclusions) located at this zone.